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Finding the Fourth Proportional to 691.68, 1,031.11 and 639.84

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Solution

The fourth proportional to 691.68, 1,031.11 and 639.84 is: 953.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    691.68 : 1,031.11 = 639.84 : x
  2. Step 2: Convert to fraction form
    691.68/1,031.11 = 639.84/x
  3. Step 3: Cross multiply
    691.68x = 1,031.11 × 639.84
  4. Step 4: Simplify right side
    691.68x = 659,745.42
  5. Step 5: Solve for x
    x = 659,745.42/691.68
  6. Step 6: Final answer
    x = 953.83

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.